The present invention relates to a SAR radar system. Such systems concern a SAR radar carried by a vehicle moving above the surface of the Earth or another planet and comprises means to obtain radar wavelength resolution images of the surface. The technique known as synthetic aperture radar--SAR--is well-known though until recently the achieved resolution has been much coarser than the wavelength. By ultra wide band, UWB, is here understood the use of a radar signal with a relative bandwidth of more than one octave. Such a large bandwidth will result in range resolution of wavelength order. A similarly high azimuth resolution calls for a radar antenna which collects signals over a wide aspect angle interval (in the regime 30.degree.-120.degree.). The antenna may either be steerable to illuminate one and the same patch on the ground as the radar vehicle passes by this patch, so called spotlight SAR, or the antenna beam may be sufficiently wide to continuously illuminate the full adopted aspect angle interval, so called strip map SAR. The combination of large relative bandwidth and a wide aspect interval for data collection enables the wavelength limit for resolution to be approached, as has been successfully demonstrated for instance in the CARABAS system, Swedish patent 8406007-8 (456 117), European patent 86900306.1 (202 320) and U.S. Pat. No. 4,866,446 and 4,965,582 all hereby incorporated by reference.
The vehicle carrying the radar may be an aircraft, an unmanned aerial vehicle, a so-called UAV, or a satellite. The radar may also be installed onboard a space vehicle for the purpose of exploring the surface of other planets.